A Twitter exchange recently revealed that certain members of the small subset of science writers who were humanities majors, also have a shared taste for classic mysteries. They thought they would co-post, on their respective blogs, some nice literary analyses ("the epistolary opening of Busman's Honeymoon ..."), but then realized that readers were no doubt bored by the overuse of epistolary openings in the science blogosphere. So they decided to write about the science of classical mystery writers instead. Links to other posts in the series by Deborah Blum, and Ann Finkbeiner -- plus me at Discovery News on Jane Langton's Dark Nantucket Noon, and an earlier post of mine on singing sands, in honor of Josephine Tey's mystery The Singing Sands -- can be found at the end of this post.

Gentleman-detective Lord Peter Wimsey is stranded in a small English village due to car trouble on New Year's Eve at the start of Dorothy L. Sayers' The Nine Tailors. This being a holiday, and one of the change-ringers being absent, he finds himself sitting in on a record-breaking, nine-hour ringing of the changes for the parish. He made an impression, so much so that a few months later, he gets dragged back to the village to help solve the mystery of a body that has turned up in the cemetery, which may or may not be connected somehow with a robbery of a pricey emerald necklace some 15 years before.

Sayers certainly did her authorial homework: the entire novel is constructed around bells and change-ringing, right down to the chapter titles and epigrams. So it's the perfect framework to discuss science of bells and change-ringing, which turns out to be a rich lode to mine indeed. (Caveat: there will be spoilers towards the end of this post, but I promise to give fair warning when we get there.)

Back before the days of insta-communication, English communities relied on the tolling of bells to sound alarms and mark the passing of village residents. Sayers took her title from the number of times a bell will toll to mark the passing of a man: nine strokes ("ringing the nine tailors"), followed by a pause, then the slow tolling of single strokes at half-minute intervals -- however many strokes required to mark the age. The pattern was similar for a woman, except there would be six initial tolls. (If "nine tailors make a man," then I guess six tailors make a woman.) If that sounds exhausting, remember that life expectancies were much lower as recently as the late 1800s -- especially for women.

The famed "bow bells" at London's church of St. Mary-le-Bow are among the most famous in the world, showing up frequently in London lore. Remember the tale of Dick Wittington? In 1932 he supposedly hard the Bow bells calling him back to London to fulfill his destiny as Lord Mayor. It is said that a true Cockney must be born within earshot of the bells, and a medieval nursery rhyme ends with the line, "I do not know says the Great Bell of Bow."

The first known historical reference to the Bow bells is in 1469, when the Common Council ordered the ringing of a curfew every night at 9 PM. A fifth bell was donated to the church in 1515 by one William Copland, a church warden, although he didn't live to see it rung. (It was rung for the first time at his funeral.)

By 1635 there were six bells, although both tower and bells were destroyed in the the Great Fire of London in 1666. The church was rebuilt with a new tower for 12 bells, although initially there were only eight; there weren't a fully 12 until 1881. They weren't rung very often, either: there were problems wit the tower, the bells and the bell frame, apparently, as well as a shortage of ringers. The BBC used a recording of the Bow bells during World War II as an interval signal for English language broadcasts. There are still 12 bells, cast at the famed Whitechapel bell foundry in 1956, after the church and bell tower were refurbished. So the bells of St. Mary-le-Bow still ring today.

Casting the Bells

Bells are fascinating things, right down to how they are made -- or rather, cast, since the process involves pouring molten bell metal into a mold. In The Nine Tailors, the tenor bell is named Tailor Paul, supposedly cast in a field next to the churchyard in 1614. Once the bell has been cast, it can be "tuned" by paring metal off various parts of the bells' soundbow.

As for the creation of the mold, that is an equally painstaking process. There is an inner mold, or core, and an outer one (the "cope), both made up of a mixture of clay, cow dung (!) and horse hair. This mud pie is built up into the desired shape, supported by a metal base plate ("strickle"), layer by painstaking layer. After a certain number of layers, the mold is baked in a dry oven until it is hard, then more layers are added, then baked, and so on. Any air pockets or moisture would be bad, as the finished mold would crack when the molten lead is poured into it.

Just before the final layer has been baked hard, the mold is coated with graphite to prevent the molten metal from burning it, and any desired inscription is stamped into the mold in reverse. This is another time-honored tradition of bells, which frequently have nicknames and inscriptions, as if they were, indeed, alive.

For instance, in Sayers' novel, the oldest bell is dubbed Batty Thomas, cast in 1380, and bears the inscription "Abbat Thomas sett mee heare + and bad mee ringe both loud and cleer." (The oldest bell hung for change ringing that is still in use was cast in 1325; it is the fifth bell at St. Dunstan's Church in Canterbury, Kent.)

Wimsey even alludes at one point to one of the most popular inscriptions employed by the Whitechapel Bell Foundry for its treble bells: "I mean to make it understood that tho' I'm little yet I'm good."

The traditional architecture of a bell tower incorporates a bell chamber with louvred windows so the sound can escape outside, instead of building up to intolerable levels within the chamber (see discussion of forced oscillation resonance in the final section, unless you want to avoid spoilers).

Below the bell chamber, there is usually at least one sound chamber, through which the ropes pass as they are dropped down into the ringing chamber. Each rope has a wooden grip, called a sally. ("Wimsey could see the eight bell-ropes, their wooden sallies looped neatly to the walls and their upper ends vanishing mysteriously into the shadows of the chamber roof.")

For full-circle ringing, a bell is hung so that it can rotate a full 360 degrees, fitted with a wheel and a rope. Traditionally, the ball begins in the "mouth down" position and must be "rung up" in order to start the tolling. ("Wimsey brought his bell up competently up and set her at backstroke while the tuckings were finally adjusted.") The ringer then has to pull on the rope repeatedly so that the bell swings higher and higher, until it rotates the full 360 degrees each time the rope is pulled.The bell winds the rope onto its wheel as it completes the rotation, such that the sallie is lifted towards the ceiling (the "handstroke"). Then it swings back in the opposite direction as the ringer pulls the tail-end of the rope towards the floor (the "backstroke").

These bells aren't easy to ring either, according to my fellow science writer Karen Fox, who has been a modern-day bell-ringer at National Cathedral in Washington, DC. In an email exchange a couple of years ago -- we were gushing over our shared love for Sayers' novel -- she said, "You have to pull it the perfect amount so it will balance upside down. Only by balancing it to give yourself a beat of time before it swings back down can you control it at all. One has to learn the feel of the weight of the bell and slow it down perfectly as it nears the top of its arc."

Ringing the Changes

Karen also said she was drawn to the numbers of the patterns in the changes. Change-ringing in England -- at least as we know it today -- evolved in the 17th century; the first textbook on change-ringing appeared in 1671 and was called Tittinnalogia, or The Art of Ringing. There are simple "rounds" that can be rung, but since this gets monotonous, over time, variations of the patterns emerged, and these are known as specific peals -- many with colorful names.

Wimsey's fictional nine-hour New Year's peal of 15,840 "Kent Treble Bob Majors." Other peals mentioned in Sayers' novel include Grandsire Triples, Steadmans, and Grandsire Major. One wouldn't confuse the sound of ringing the changes with anything resembling "music" as the term is traditionally used, however. (You can listen to some recordings here.)

"The art of change-ringing is peculiar to the English and, like most English peculiarities, unintelligible to the rest of the world. To the musical Belgian, for example, it appears that the proper thing to do with a carefully-tuned ring of bells is to play a tune upon it. By the English campanologist, the playing of tunes is considered to be a childish game, only fit for foreigners; the proper use of bells is to work out mathematical permutations and combinations."

This is partly a limitation of the bells: they have a lot of momentum, they're huge, and it takes about two seconds for them to rotate fully, so it's far too challenging to play melodies with them. But leave it to the Brits to take a shortcoming and turn it into its own peculiar art form. Maybe the bells can't easily play a tune, but they can be rung in succession, in various changing sequences. Each bell can only be moved one time in the sequence.

Quoth Karen: "Part of the reason the patterns are limited to only changing order with your neighbor at any given time is due to that momentum thing. You can get the bell to stop just long enough to switch positions with the person before or after you, but no longer. That's why you never hear melodies with change-ringing." (You can find an Applet of change-ringing here.)

For instance, if you ring the bells in order -- from the lightest, highest pitched bell to the heaviest -- this is known as "rounds," denoted by a row of numbers.

A "simple plain hunt," per Karen, would be 1-2-3-4-5-6, followed by the next row (2-1-4-3-6-5), and the next, and the next (2-4-1-6-3-5, 4-2-6-1-5-3, 4-6-2-5-1-3, etc.), "because no bell could possibly ring further than one spot away from where they rang in the last round."

(A notation of rounds of the Plain Bob Minor peal is pictured at right.)

Sayers includes a nice summation of the peculiar aesthetics of campanology in The Nine Tailors:

To the ordinary man, the pealing of bells is a monotonous jangle and a nuisance, tolerable only when mitigated by remote distance and sentimental association. The change-ringer does, indeed, distinguish musical differences between one method of producing his permutations and another; he avers, for instance, that where the hinder bells run 7, 5, 6 or 5, 6, 7, or 5, 7, 6, the music is always prettier, and can detect and approve, where they occur, the consecutive fifths of Tittums and the cascading thirds of the Queen's change.

But what he really means is, that by the English method of ringing with rope and wheel, each several bell gives forth her fullest and her noblest note. His passion -- and it is a passion -- finds its satisfaction in mathematical completeness and mechanical perfection, and as his bell weaves her way rhythmically up from lead to hinder place and down again, he is filled with the solemn intoxication that comes of intricate ritual faultlessly performed.

Killer Bells?


In fact, Sayers makes ingenious use of change-ringing and its notation as a plot device: a letter is discovered in the bell chamber with the body, but the text appears to make absolutely no sense. Then Wimsey, with the help of the vicar, realizes that it's written in code -- and the key to that code is a specific peal written out in change-ringing notation. The decoded letter reveals the hiding place of the stolen emeralds.

Bells can be fatal, most commonly because ringers get tangled in the ropes and accidentally hang themselves, or the bells unexpectedly swing down and squash somebody's noggin. This still occasionally happens even today. In May 2008, the Independent reported that a bell ringer broke his collarbone after getting tangled up in a rope at the top of a church tower.

Apparently the rope got caught in a bunch of keys attached to his trousers, and the guy was hoisted a good three feet off the belfry floor, blacked out, and fell back to the floor. Firefighters had to rig up a pulley system to lower the injured bell ringer through a trap door in the floor, since the only other entry was up a narrow wooden spiral staircase.

Both those fates figure in the mythology of Sayers' fictional bell, Batty Thomas, which the church sexton, Mr. Godfrey, deems "an unlucky bell." Batty Thomas is blamed for the death of one of Cromwell's soldiers who ventured into the belfry and -- because the bells had been left mouth up -- when his cohorts started to pull on the ropes, Batty Thomas swung down and killed him instantly.

A few centuries later a beginning ringer tried to raise Batty Thomas alone, without help, and hung himself in the ropes. But Sayers came up with an especially ingenious theory of how her murder victim died. Wimsey's breakthrough occurs very late in the book, when he ventures into the bell tower as the bells are being rung in the midst of a major flood in the area. Sayers writes:

"He was pierced through and buffeted by the clamour. Through the brazen crash and clatter there went one high note, shrill and sustained, that was like a sword in the brain. All the blood of his body seemed to rush to his head, swelling it bursting point.... It was not noise -- it was brute pain, a grinding, bludgeoning, ran-dan, crazy, intolerable torment.... His eardrums were cracking; his senses swam away. It was infinitely worse than the roar of heavy artillery."

Wimsey manages to stagger to safety, but not before blood runs from his nose and ears. And he concludes that the bells murdered the victim; he had been tied up and forgotten during the nine-hour peal, and the noise had proven to much for his body to withstand: "I believe it is at St. Paul's Cathedral that it is said to be death to enter the bell-chamber when a peal is being rung."

Indeed, at the inquest the medical examiner testifies that the victim's brain showed evidence of "an effusion of blood into the

cortex." (Photo at left features the late actor Ian Carmichael as Lord Peter Wimsey in a 1970s TV adaption of The Nine Tailors.)

This is probably the most criticized aspect of Sayers' excellent mystery. It's an ingenious cause of death, but is it plausible? Well, bells undeniably have a natural resonance. Lots of factors contribute to the sound a bell makes -- its diameter, weight, profile, and thickness, for example -- which is why there are so many different bell profiles.

Because of that complex shape, what we hear when the bell is struck is a combination of notes, arising from different parts of the bell vibrating at different frequencies ("partial tones"). The partial tones combine in the end to give a bell its distinctive tone. Indeed, Sayers' fictional jewel thief, Nobby Cranton, stumbles upon the body in the belfry and in his haste to leave, drops his flashlight, which hits one of the bells hanging below. "I'll never forget the sound it made," he tells the Superintendent. "It wasn't loud, but kind of terribly sweet and threatening, and it went humming on and on, and a whole lot of other notes seemed to come out of it, high up and clear and close."

Every material object has a natural resonant frequency at which it vibrates -- like crystal wine glasses. Pump in more energy of the same resonance and let it build up, and the crystal wine glass will vibrate so strongly that it can shatter -- a phenomenon known as forced oscillation resonance. In order for this to work, the sound must be loud (at least 90 decibels) and prolonged (at least several seconds) to allow enough vibrating energy to build up to cause the crystal wine glass to shatter.

And of course, the sound in question must resonate perfectly with the natural resonant frequency of the glass. If it doesn't, the glass won't shatter no matter how long and loud the note in question. Furthermore, wine glasses have a unique "bell" shape that makes them especially able to propagate resonant vibrations -- and thus more vulnerable to shattering. That said, those famous Memorex commercials showing Ella Fitzgerald shattering a crystal glass with her voice was a bit of a cheat: they specifically used glasses with a high lead content (which vibrates better) and amplified her voice to about 94 decibels, on a par with a jackhammer.

I haven't been able to find any specific studies to back up or debunk Sayers' ingenious murder weapon. The best answer I could find was in response to the question of whether sound can kill comes from Cecil Adams' Straight Dope. I verified the salient points, to wit: the pain threshold in the ear is between 130 to 140 decibels -- about the same as a jet engine at close-ish range.

The eardrum will rupture around 160 decibels, or 185 decibels for "nonperiodic blast pressure." The latter is the kind of sharp instantaneous rise in ambient atmospheric pressure resulting from an explosion or the firing of a large weapon -- or a thunderclap or sonic boom, for that matter. Sound, after all, is a pressure wave.

Sound, apparently, can kill. Sometimes. In World War I, for instance, soldiers were found dead in the vicinity of an explosion, yet they didn't have any obvious external injuries -- just major internal damage, especially to the ear, lungs and gastrointestinal tract. The prevailing theory as to cause of death is an air embolism, starting in the lungs. The immense pressure of the blast pushes on the chest and ruptures the delicate lung tissue, so air bubbles can travel into the arteries and thus to the heart, brain and other organs. The result is, obviously, death.

The military is interested in the development of acoustic weapons for that very reason. Adams cites German physicist Jurgen Altmann's treatise on the physiological effects of high-intensity sound, who concluded that "the threshold for suffocation or embolism following lung rupture is 2.6 to 11 times atmospheric pressure, depending on pulse duration."

Could the bells in Sayers' novel have produced those extremes of pressure? Wimsey admits he couldn't know what, exactly, the cause of death might be -- "stroke, apoplexy, shock" -- but the victim was tied up there for the full nine-hour New Year's Eve peal on a night "when the snow choked the louvres and kept it pent up in the tower," making the noise even worse. And of course, if the victim had a pre-existing medical condition, it would be far easier for him to have suffered some sort of seizure and died -- although the evidence for this sort of thing remains hotly disputed.

Barring any better explanation, I'll just side with Sayers' fictional Superintendent: "Matter of periods of vibration, I suppose." Case closed. For now.

Check out these related posts!

The Science of Mysteries: Instructions for a Deadly Dinner (Deborah Blum on Dorothy Sayers' Strong Poison)

The Science of Mysteries: Watch Where You Fall In (Ann Finkbeiner on Josephine Tey's To Love and Be Wise)

The Science of Mysteries: Total Eclipse of the Heart (Jennifer Ouellette at Discovery News, on Jane Langton's Dark Nantucket Noon)

The Science of Mysteries: Of Granular Materials and Singing Sands (Jennifer Ouellette on Josephine Tey's The Singing Sands)